A light-emitting diode (LED) is suitable for various lighting and display applications because it has good opto-electrical characteristics of low power consumption, low heat generation, long life, shock tolerance, compact, and swift response. A multi-cell light-emitting device is a device composed of multiple light-emitting diodes, such as an array of light-emitting diodes. With the development of technology in applications, a multi-cell light-emitting device has a wider application in the market, for example, an optical display device, a traffic light, and a lighting apparatus. A lighting device of a High Voltage LED (HV LED) is one of the examples.
As shown in FIGS. 7A and 7B, a conventional array of light-emitting diodes 1 includes a substrate 10, a plurality of light-emitting diode units 12 arranged in two-dimension on the substrate 10, wherein each of the light-emitting diode units 12 includes a light-emitting stack comprising a p-type semiconductor layer 121, a light-emitting layer 122, and an n-type semiconductor layer 123. These light-emitting diode units 12 are formed by patterning a light-emitting stack with an etching process to form trenches 14 by which the light-emitting diode units 12 are defined. Since the substrate 10 is not conductive, trenches 14 formed between the plurality of the light-emitting diode units 12 make the light-emitting diode unit 12 electrically insulated from each other. Further, the light-emitting diode units 12 are partially etched to expose the n-type semiconductor layer 123, and a first electrode 18 and a second electrode 16 are respectively formed on the exposed region of the n-type semiconductor layer 123 and a p-type semiconductor layer 121. Then based on a circuit design, conductive wiring structures 19 are used to form connection between the plurality of light-emitting diode units 12, the first electrode 18, and the second electrode 16, and the plurality of light-emitting diode units 12 is electrically connected in series or in parallel. For example, if a serial circuit is formed, a Direct Current (DC) High Voltage LED (HV LED) is formed.
Nevertheless, a device formed by this process often has a decreased overall luminous intensity because of the light absorption between the light-emitting diode units 12. In addition, for a device formed by this process, the light-emitting diode units 12 are formed by patterning a light-emitting stack with an etching process to form the trenches 14 by which the light-emitting diode units 12 are defined. Therefore, different devices includes different light-emitting diode units 12 from different parts of the substrate, and there is a poor uniformity between devices on optical characteristics or electrical characteristics.